In the future, research may reveal an optimal time of day to take pills, have surgery or undergo chemotherapy.

In the future, research may reveal an optimal time of day to take pills, have surgery or undergo chemotherapy.

This emerging strategy is called chronotherapy, and it is growing. Studies suggest that certain types of chemotherapy should be given in the morning or evening; kidney dialysis patients tend to fare better if they receive their treatment in the morning; and certain blood pressure medicines work better in the morning and others at night.

A prescription for a good night's sleep may accompany chronotherapy practices.

Adequate sleep seems to affect the body's immune response. In a small study published in 2002 in the Journal of the American Medical Association, sleep researcher Eve Van Cauter found that flu shots might not work as well in people who are tired. She gave flu shots to 11 healthy young men who had slept four hours a night for four straight nights. The men produced only half as many flu-fighting antibodies compared with people who slept normally before receiving the shot.